package org.apache.solr.search;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.util.OpenBitSet;

import java.io.IOException;

/**
 *
 */

public class DocSetCollector extends Collector {
	int pos = 0;
	OpenBitSet bits;
	final int maxDoc;
	final int smallSetSize;
	int base;

	// in case there aren't that many hits, we may not want a very sparse
	// bit array. Optimistically collect the first few docs in an array
	// in case there are only a few.
	final int[] scratch;

	public DocSetCollector(int smallSetSize, int maxDoc) {
		this.smallSetSize = smallSetSize;
		this.maxDoc = maxDoc;
		this.scratch = new int[smallSetSize];
	}

	@Override
	public void collect(int doc) throws IOException {
		doc += base;
		// optimistically collect the first docs in an array
		// in case the total number will be small enough to represent
		// as a small set like SortedIntDocSet instead...
		// Storing in this array will be quicker to convert
		// than scanning through a potentially huge bit vector.
		// FUTURE: when search methods all start returning docs in order, maybe
		// we could have a ListDocSet() and use the collected array directly.
		if (pos < scratch.length) {
			scratch[pos] = doc;
		} else {
			// this conditional could be removed if BitSet was preallocated, but
			// that
			// would take up more memory, and add more GC time...
			if (bits == null)
				bits = new OpenBitSet(maxDoc);
			bits.fastSet(doc);
		}

		pos++;
	}

	public DocSet getDocSet() {
		if (pos <= scratch.length) {
			// assumes docs were collected in sorted order!
			return new SortedIntDocSet(scratch, pos);
		} else {
			// set the bits for ids that were collected in the array
			for (int i = 0; i < scratch.length; i++)
				bits.fastSet(scratch[i]);
			return new BitDocSet(bits, pos);
		}
	}

	@Override
	public void setScorer(Scorer scorer) throws IOException {
	}

	@Override
	public void setNextReader(IndexReader indexReader, int docBase)
			throws IOException {
		this.base = docBase;
	}

	@Override
	public boolean acceptsDocsOutOfOrder() {
		return false;
	}
}
